DESCRIPTION (provided by investigator): Human papillomaviruses (HPVs) are the most common sexually transmitted viral infections, resulting in genital warts, intraepithelial neoplasia and anogenital cancers. Diagnosis and treatment of HPV-associated disease is extremely costly. The recent introduction of prophylactic vaccines has the potential to greatly reduce infection and disease caused by the two types responsible for approximately 70 per cent of cervical cancers, HPV 16 and 18, and the quadrivalent vaccine, which also includes HPVs 6 and 11, can prevent up to 90 per cent of genital warts. However, the relatively modest uptake of the vaccine, especially in the developing world, and the very high fraction of men and women who are already infected, means that HPV-associated disease will remain a significant public health problem for decades. Thus, continuing to better understand the natural history of genital HPV infection and the basis for a protective immune response is an important goal. The development of serologic assays to detect HPV antibodies has allowed an assessment of the prevalence of HPV infection, which complemented estimates of active infection made on the basis of detecting HPV DNA in genital tract specimens. The assays have improved in sensitivity, and multiplexing methods now make it possible to measure antibodies to dozens of HPV types, as well as defining immunoreactive epitopes. In aim 1, we will use the multiplex assay to examine the prevalence of 20 HPV types in sera from our existing cohorts of young women and men, for whom there are repeated serological, HPV DNA, and sexual behavior measures. The goal of aim 2 is to develop even more sensitive serologic assays by employing a new technology in which the detection of antibody is greatly increased by coupling the anti-human antibody with a DNA tag that is amplified by PCR. Detection of HPV low levels of HPV antibodies in serum, oral exudates and cervical lavage will provide new tools and insights into the natural history of infection. Aim 3 will examine the epitopes on the HPV 16 virion that elicit antibodies, using an approach in which the type-specific surface exposed loops have been swapped for the corresponding residues of HPV 31. It is of particular importance to characterize the differences in antibody reactivity induced by natural infection compared to vaccination. By understanding the basis of the HPV 16:31 cross-reactivity it may be possible to engineer more broadly protective vaccines. Aim 4 provides a unique opportunity to characterize HPV antibody maturation over time. Vaccination stimulates a large number of naove B cells that can be identified using Solexa sequencing technology to sequence segments of the rearranged V(D)J immunoglobulin genes, coupled with computational analyses. By vaccinating HPV 6,11, 16, 18 naive men and examining their B cell repertoire over time it will be possible to identify HPV-responsive clones and the somatic hypermutation that results to improve antibody binding. Taken together these studies will provide important new information on the prevalence of genital HPV infections and new insights into the basis of protection against HPV infection.